1. Field of the Invention
The present invention relates in general to on-line sampling and analysis of a solid particulate suspended in a fluid, such as a phosphate rock, other minerals, grains, seed and other solids suspended in water, air, or other liquids or gases. More particularly, the invention relates to positioning a vortex tube in a process stream above a sample presentation area such as a light transparent window for removing deposited particulates, such as phosphates, and allowing for the collection of subsequent samples, in which the vortex tube provides a bypass to return the particulate samples to the flow downstream of the sample presentation area for continuous operation without interruption of the flow in the sampling line.
2. Description of the Related Art
Presently, phosphate rock is recovered from a sand-clay mixture that is mined from mineral deposits. Industrial recovery of solids of a few millimeters or less, such as phosphate rock, e.g.,  less than 1 mm, begins with chemical treatment of a liquid aqueous slurry which includes a long chain hydrocarbon liquid. These hydrocarbons attach to the phosphate rock and are hydrophobic in nature. Thus, after they attach to the rock, the phosphate rock is forced out of the water phase to the surface in an aeration tank called a flotation cell. The flotation cell must be monitored to ensure maximum recovery of the phosphate rock. The phosphate content in the slurry exiting the flotation cell after the removal of the hydrocarbon-bound phosphate rock, also known as tailings, is a representative indicator of flotation cell performance.
Phosphate rock found in the tailings is considered unrecoverable and a lost natural resource. Normal operation of the flotation cell involves operator estimation of cell performance by visual inspection of the tailings. To optimize the operator""s control of the flotation cell, it would be desirable therefore to provide a system and a method of continuously monitoring phosphate tailings to provide feedback to the operator to improve the performance and efficiency of the flotation cell operation. To this end, it is usually desirable to maintain the %BPL content in the tailings streams below 3% for acceptable cell performance.
U.S. Pat. No. 5,396,260 to Adel et al. for xe2x80x9cVideo Instrumentation for the Analysis of Mineral Content in Ores and Coalxe2x80x9d issued Mar. 7, 1995, discloses the determination of mineral content using a video system in which digitized images having assigned gray levels are analyzed to determine the content of particular minerals in a coal slurry determined from the distribution of the gray levels. Slip streams are extracted from the tailings and feed lines which are allowed to pass through a thin sample chamber with flat glass plates on either side, the sample chamber being enclosed in a light type box with a video camera to provide a reflected light image for sample analysis. However, such slip streams extracted from the tailings and feed lines, are not in line with the tailings stream but merely tapped away from the fluid media being processed and may not be representative of the sampling of an on-line flowing slurry.
U.S. Pat. No. 4,797,550 to Nelson et al. for xe2x80x9cFiber Optic Detector for Flotation Cell Processingxe2x80x9d issued Jan. 10, 1989 discloses a fiber optic detector submerged in a coal slurry to monitor a coal separation process. Light transmitted by an optical fiber is directed toward the slurry, and thus scattered by the slurry, from which a portion of the light is deflected back to the fiber optic detector, from which the light intensity reflected by the slurry is used to detect the mineral content in the slurry. Accordingly, only a small sample separated from the slurry is analyzed, which may not be representative of the on-line stream.
It would be desirable therefore to provide on-line sampling in which sampling of the particulate content in a fluid media is provided in-line with the process stream to collect representative particulate samples, such as phosphate rock and sand in a tailings line. An in-line sample presentation assembly would be advantageous for the collection of samples from the tailings where the sample could be returned to a slurry stream for continuous operation without interruption of the flow in the sampling line.
Typical particulate analysis techniques provide off-line analysis or tapping of relatively small representative samples of the particulates suspended in a fluid media. These are often difficult to correlate to current process conditions from the resultant data. An on-line analyzer provides faster and better feedback for adjusting process control parameters. The apparatus and method embodying the present invention provides on-line sampling and analysis of the content of a particulate composition having a particle size from about 0.1 to about 20 mm, which is suspended or slurried in a fluid, which may be a liquid or a gas, to provide a rapid analysis of the particulate composition. The use of the fluid stream discussed herein is generic to gas and liquid carrier media. In an important aspect, the invention provides a method and apparatus for the analysis of the phosphate rock content values in a flowing slurry stream. The phosphate analyzer is provided in-line with the tailings stream of a phosphate floatation process.
In one aspect, the method of invention employs visual light and a visual light characterizing detection device which uses a visual image of the particulates, such as grains or seed in suspension or a phosphate tailings slurry, to analyze the particulate sample. The on-line sampling apparatus collects and presents samples that are rapidly purged and resampled using a procedure in which particulate solids in a fluid stream in gas or liquid are accumulated, concentrated or packed in a vessel or container for in-line analysis. In another aspect the characterizing detection device used to analyze the samples may use X-ray, gamma-ray, neutron, alpha particle, or other radiation sources other than visual light where a sample is presented on an area not transparent to visual light, but which is transparent to the energy source. In a further aspect the characterizing detection device may employ magnetic, acoustic, ultra-sound, or other energy sources where the particulate sample is presented in a sample presentation area which is analyzed with the particulate sample packed for the application of the associated energy or force. Analysis using electromagnetic energy such as X-ray, ultra-violet, infra-red or other radiation sources other than visual light requires a sample presentation area with a window transparent to the energy being used. Another important aspect provides optical image analysis using a video camera normal to the sample deposited on the sample presentation area using a computer providing image processing of the samples. To capture this image, an in-line mechanical delivery vortex assembly presents a representative sample to a video camera. The invention provides a uniform, stationary, and quickly removable particulate sample which is trapped and imaged by positioning a vortex tube in the process stream above the particulate sample presentation area for thereafter removing deposited particulates. The invention allows for the collection of subsequent particulate samples, in which the vortex tube provides a bypass to return samples to the flow downstream of the sample presentation area. In the invention, the particulate sample being analyzed is taken from the continually flowing stream of particulates suspended in the fluid media to provide a representative particulate sample without interruption of the flow.
According to the invention, the in-line analysis system introduces a sample of suspended or slurried particulate composition, such as a sand, phosphate, and water slurry stream into a vortex assembly. The slurry stream gravitationally deposits a particulate layer, such as sand and particulate phosphate on the bottom of the vortex assembly, which can be viewed through a quartz imaging window. In an important aspect this window is a substantially planar surface to present a sample which has a planar surface to the characterizing detection device. Pressure-inducing piping, located downstream of the vortex assembly slightly restricts the flow of this stream, yet permits an uninterrupted flow of slurry through the system while allowing the deposited sample to be stationary for optical detection or analysis during each sampling cycle. In an important aspect, analysis is done by an imaging technique. When a new sample and sample image is needed, the deposited layer is removed by opening a bypass line around the pressure restriction. The pressure released causes a vortex that removes the old sample and allows a subsequent portion of the flow stream to be sampled. When the bypass valve is closed, the new sample is quickly and uniformly gravitationally deposited on the quartz viewing glass.
In one aspect, the particulate layer, such as sand and phosphate, is deposited on the quartz sample presentation area which is transparent or pervious to light. The sample is imaged through this viewing glass with a black-and-white or color video camera. The camera captures still images for analysis, and when a new image is required, the bypass valve is opened and closed again. The signal from the camera is captured by a frame grabber computer card which translates the picture into a pixel matrix image. The computer software determines the average pixel gray-scale or color value, which is compared with a standard associated with phosphate content. To verify the correlation, the computer also analyzes individual particle sizes, which information is used to correct the standard for shifts in gray-scale or color of the particulates which in the case of phosphates, the sand and slurry matrix may change continuously due to the nature of mineral deposits. A computer-user interface is provided for displaying the current image, the analyses information, such as calculated phosphate content, particle size information, and historical trends.
The invention provides an on-line sampling and image analysis apparatus for analyzing various compositions of fluid media having suspended particulates. The fluid media may be a gas, or in an important aspect, a liquid such as water, and the particulates may include rock, sand or other solid particle content. A media flow director such as the vortex assembly directs the media over the sample presentation area to remove the deposited particulates.
In an important aspect, an on-line sampling and image analysis system has an inlet pipe for receiving a continuous flow of a slurried particulates. A sample presentation area is positioned below the flow of the slurry in an assembly allowing for the depositing of a sample of particulates from the slurry which is collected for viewing by a computer controlled video camera. Gravity settles the particles onto the sample presentation area. The camera images the sample of the particulate solid deposited on the sample presentation area which is a light transparent window, and a personal computer analyzes images provided by the camera to characterize the particulate composition in the fluid media. A vortex tube positioned in the flow of the slurried particulate through the assembly, and above the sample presentation area, generates a vortex for removing the sample of the particulates deposited on the sample presentation area, allowing for the collection of a subsequent sample from the slurry at the sample presentation area. The vortex tube is coupled with associated bypass piping to remove the particulate sample from the flow, or to return the particulate sample to the flow of the fluid slurry downstream of the sample presentation area for continuous operation without interruption of the flow in the sampling line. The personal computer provides a user interface for monitoring the phosphate content of the slurry.
Briefly summarized, the present invention is directed to an on-line particulate sampling and analysis system and method in which a sampling line inlet pipe receives a flow of a liquid or gas fluid media having a particulate solid content suspended therein. A sample presentation area is positioned below the flow of the fluid media in an assembly allowing for the depositing of a sample of the particulates from the fluid media. The sampled solid content is thus collected for viewing in order to characterize the particulate solid in the fluid media. In an important aspect, a vortex tube positioned above the sample presentation area generates a vortex for removing the particulate sample deposited on the sample presentation area, allowing for the collection of another particulate sample from the fluid media at the sample presentation area. The vortex tube may be coupled with associated bypass piping to remove the particulate sample from the flow, or to return the particulate sample to the flow of the fluid media downstream of the sample presentation area for continuous operation without interruption of the flow in the sampling line.
It is an object of the present invention to provide analysis on-line sampling and analysis of a particulate solid content suspended in a fluid media that overcomes the disadvantages and problems of the prior art.
It is another object of the invention to provide an on-line sampling and image analysis system and method for particulate solids, such as the phosphate content in a process stream.
It is a further object of the invention to provide positioning of a vortex tube in a process stream above a sample presentation area for removing deposited particulates allowing for the collection of subsequent particulate samples.
It is yet another object of the invention to provide a vortex tube coupling to a bypass pipe to remove the particulate sample from the flow, or to return particulate samples to the flow downstream of the sample presentation area for continuous operation without interruption of the flow in the sampling line.
Other objects and advantages of the present invention will become apparent to one of ordinary skill in the art, upon a perusal of the following specification and claims in light of the accompanying drawings and appendix.